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The Central Public Health Laboratory at Colindale co-operated
in establishing the cause of the outbreak. All the persons affected
had eaten cold sliced salt beef, samples of which were found to
contain the bacteria Clostridium Welchii, as did 24 faecal specimens
from the persons affected.
As a result of this outbreak I convened a conference with Dr.
Betty Hobbs, the Food Bacteriologist from the Central Public Health
Laboratory, the Bacteriologist employed by a large food firm, the
Chief Chemist of the same firm and the Borough Senior Sanitary
Inspector, to see what measures could be taken to prevent a recurrence
of this type of food poisoning. I also talked to the Area
School Meals Organiser and as a result of these discussions the
following points emerged:—
(1) The method of salting meat in brine tanks should, if
possible, be standardised with the brine strength not less
than 20% as measured by a hydrometer (concentrations of
less than 20 % are not effective in inhibiting the growth
of bacteria).
(2) Thorough cooking and rapid cooling of joints of meat is
essential to prevent the multiplication of food poisoning
bacteria in the interior but this is difficult unless the joints
are cut so that they weigh not more than 6 lbs.
(3) The process of boning and rolling meat allows the introduction
of surface contamination into the joint.
Even prolonged boiling may be insufficient to kill heatresistant
spores of bacteria such as Clostridium Welchii at
the centre of the meat.
(4) Rapid cooling is essential immediately after cooking or the
surviving spores develop quickly in conditions of warmth
and sufficient bacteria to cause illness are produced. This
rapid and thorough cooling cannot be guaranteed unless the
joints are placed on wire cooling trays and electric fans arc
used in addition.
(5) In canteens meat should be cooked and eaten the same day,
but if this is impracticable with the present methods of
cooking, then pressure cooking should be used instead.
These points were included in a complete report on the whole
outbreak of food poisoning which was sent to the Minister of Health.
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